City Research Online

Abstract

In this paper, the potential influence of near-fault effects and of the incident angle of earthquake waves to the seismic response of a typical jack-up offshore platform is assessed by means of incremental dynamic analysis involving a three dimensional distributed plasticity finite element model. Two horizontal orthogonal strong ground motion components of a judicially chosen near-fault seismic record is considered to represent the input seismic action along different incident angles. The fault-normal component exhibits a prominent forward-directivity velocity pulse pulse-like) whose period lies close to the fundamental natural period of the considered structure following a “worst case scenario” approach, while the fault-parallel component does not include such a pulse. Pertinent numerical data demonstrate that the fault normal component poses much higher seismic demands to the “prototype” jack-up structure considered compared to the fault parallel component. Further, significant variation in the collapse resistance/capacity values is observed among different incident angles especially for the “critical” fault normal component. It is concluded that the combined effect of forward-directivity phenomena and the orientation of deployed jack-up platforms with respect to neighbouring active seismic faults needs to be explicitly accounted for in site-specific seismic risk assessment studies. Further research is warranted to propose recommendations on optimum orientation of jack-up structures operating in the proximity of active seismic faults to minimize seismic risk.

Publication Type:	Conference or Workshop Item (Paper)
Publisher Keywords:	Near-fault seismic ground motions, forward directivity pulses, incremental dynamic analysis, seismic incident angle
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Departments:	School of Science & Technology > Engineering

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